In the early development of the motion picture, as described in an article entitled "Home Movies" which appeared in the Super 8 Film Maker, May/June 1974 by Lenny Lipton, experimentation was conducted to determine the ideal parameters. Perhaps the foremost innovator was Thomas Edison who designed the 35 mm format which is still the most widely used theatrical motion picture format worldwide. Edison chose a frame rate of 48 fps (frames per second), which is a rate that was found to avoid observable flickering. However, this rate was later abandoned by the industry as a result of the work of Louis and August Lumier who discovered that flashing each frame a plurality of times can eliminate flicker. They chose a 16 fps rate, but with each frame flashed three times (two interruptions to provide three brief showings) to obtain a 48 per second flashing rate which was found to avoid observable flickering while reducing the required amount of film stock.
Psychologists have observed a "Phi Phenomenon", wherein an illusion of motion is observed when at least about 14 or 16 fresh images or frames per second are shown. Another observed phenomenon is the "persistence of vision" or "critical fusion frequency" phenomenon, wherein flicker is no longer sensed when the images are flashed at a frequency of at least 48 per second. These phenomena are discussed in "Motion Picture Work" by Hulfish pages 81-83, and an article entitled "Is the 18 fps `Amature` Speed Acceptable for Professional Use?" which appeared in the Super 8 Film Maker, by Lenny Lipton. Thus, when 16 fresh frames are shown each second, but with each frame flashed three times, both the "phi" and "critical fusion" requirements are satisfied, and a substantially continuous and flicker-free motion picture image can be observed (at least when the picture quality is not very good). In fact, 16 fps with 3 flashes per frame, became the standard in silent films (such films often appear jerky when shown nowadays, but only because modern equipment shows them at 24 fps with double flashing).
When sound was added to motion pictures in the late 1920's, a faster film speed was needed so the sound track could move fast enough past the sound head to generate good sound fidelity. A rate of 24 fps with double flashing of each frame, which provides 48 flashes per second, was chosen as the standard. This rate has continued from that time to the present, and remains the worldwide standard for commercial theater motion picture projection. Although considerable development work has been done on improving motion picture quality, relatively little has ever been published regarding frame rates since the 24 fps double flash rate standard was adopted; in fact modern articles which have been found on the subject suggest that frame rates of less than 24 fps but with triple flicker should be considered for modern use. It may be noted that very high camera frame rates are sometimes used in scientific experimentation, such as in investigating the impact of a projectile or the flight techniques of birds, but the resulting film is shown at a much lower rate such as 18 fps or 24 fps, but not at the original camera rate. It also may be noted that the use of changeable frame rates of as high as 54 fps has been mentioned in U.S. Pat. No. 3,788,736 by Oulevay. However, he uses this rate because his shutter is open for a fixed percent of every cycle, since it does not have a variable shutter such as are used in professional motion picture cameras used to create commercial theater-quality motion pictures.
Considerable development work has been performed on improving image quality. The graininess of film limits its resolution. Graininess probably was not a problem in the earliest motion picture development by Edison whose development was concerned with peep show display (the nickelodeon). Even in early theatrical display, the problems of accurately aligning subsequent film frames and other technical limitations probably overwhelmed film resolution limitations, as discussed in "A Million and One Nights, A History of The Motion Picture", page 143, by Terry Ramsaye published by Simon and Shuster (1926). However, as camera and projector technology improved, the film resolution limitations have become important, especially as bigger and wider screens have been employed. Wider screens that provide a greater horizontal angle of view have long been recognized as desirable in providing greater realism, but they can result in increased lateral magnification which increases the noticeable graininess. 70 mm wide film was developed in the early 1950's to increase resolution. A technique named Vista Vision was developed in the late 1950's for the wide screen, wherein standard 35 mm film was used but each frame was positioned at a 90.degree. rotation from normal; thus, instead of using standard film frames 0.825 inch wide and 0.446 inch tall, Vista Vision used frames about 0.870" tall and about 1.470" wide (with the 1.470" dimension extending along the length of the film). A technique named Cinerama was developed in the 1950's, wherein three separate projectors using 35 mm film, were used to obtain good image quality over a very wide screen. Presently, 70 mm wide film is occasionally used in commercial entertainment film projection, with an image area of 1.912 inch by 0.870 inch. While these techniques have produced clear, large images in commercial theaters, an even greater degree of realism would be desirable.